132 EVOLUTION AND MAN S PLACE IN NATURE 



mechanical forces. We are not to be misled by the 

 title Experimental Psychology. That the pheno 

 mena of nerve action bring observational science into 

 relation with the action of a rational nature is clear ; 

 but this relation implies difference. While all the 

 phenomena of nerve action are included under experi 

 mental psychology, all the phenomena of conscious 

 ness are excluded from this field of observation. This 

 separation is proclaimed in the mode of inquiry 

 essential to experimental psychology. Experiments 

 by electric excitation of the sensori-motor system 

 contirm this ; as do all experiments depending on 

 use of mechanical contrivances. The region of inquiry 

 is restricted to organism ; the mode of inquiry is 

 restricted to external observation. So long as we deal 

 with molecular movements, it is clear that speed or 

 rate of movement is calculable, if only an instrument 

 be constructed sufficiently sensitive to record results. 

 When we turn attention to contraction and expansion 

 of muscles, observation becomes more simple, because 

 the structure is visible to all, as it is more massive. 

 In these relations, a wide and deeply interesting field 

 of observation has been opened up. The larger 

 portion of it is concerned with organism ; but it bears 

 witness, so far as external bodily movements can do 

 so, to phenomena of consciousness, connected with the 

 phenomena of organic life, but unexplained by them. 

 The limits of electric excitation strictly define the 

 line of severance. Here, as elsewhere, observational 

 science lays down its own boundaries. 



Within the territory of physiology lie all the 

 phenomena of reflex action. These belong to organic 

 life of every grade. Beyond these, in human life, there 



